From: Jack Erbes <jack@vom.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Tool and Cutter Grinding
Date: Tue, 29 Dec 1998 08:04:22 -0800
Kurt Laughlin wrote:
<snip>
> I am neither a machinist nor even an operator. I'm an engineer (no
> calluses, all ten fingers :-)) who bought a small lathe and a mill-drill to
> play around with. Hand sharpening is beyond my skills, a machine sharpener
> beyond my budget, so I pay a guy to do it just buy new ones.
Once someone showed me the tricks it was pretty easy. But I don't hand
sharpen small drills (< 3/8"?).
Hold the drill in your left hand, the front side of your finger gently
touching the edge of the tool rest, with just enough drill sticking out
that it is a few thousandth's away from the grinding wheel. The cutting
edge is on the left, horizontal, and you are looking down on it.
The right hand holds the drill shank and controls infeed and the
swinging and rolling movement that follows. Gently press in until the
wheel starts cutting and at that time swing your right hand to the left
slightly, roll the drill clockwise a little, and maybe lower the end of
the drill a little as you finish the cut. The infeed is continued
enough to maintain a light cut during the entire process.
The rolling and swinging movement causes the cutting edge to move away
from the wheel as the infeed and left swing follows the relief angle
behind the cutting edge.
To practice the movement, place a properly ground large drill near or
gently touching a *non turning* wheel and make a movement that keeps the
relieved area behind the cutting edge in contact with the wheel
continuously.
It you started with a chipped point (I know, it only happens when
someone else has been using your tools), make two or three light passes
on the chipped side, then two or three on the good side and keep that up
until the chip is gone. Hold the drill up vertically towards a light
source and use a drill gage or protractor to compare the length of the
two cutting edges.
The disclaimer: Your hands, fingers and face are at some risk during
the process, use appropriate safeguards. Working around machinery is
almost as dangerous as driving on public roads or living in the world.
--
Jack in Sonoma, CA, USA (jack@vom.com)

From: Robert Bastow <Teenut@hotmail.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: sharpening drill bits
Date: Sun, 21 Feb 1999 00:18:03 GMT
John Kunkel wrote:
> For identical angles and rakes you can't beat a machine.
No you can't..and I never said you could!
> All this talk of he-man eyeball sharpening, sorry but I'm skeptical.
A. That's because you never took the time, or ever had the need to learn!
B. Anything beats throwing away a perfectly good drill just because it is blunt
C. Not everyone can justify, afford or even NEEDS a drill grinder.
I think that there is a lot of misperception as to the true uses and usage of a
drill bit. People expect and seem to need them to drill a dead size hole and
quite frankly that is a bit unrealistic for most people and NOT the way to
arrive at an accurate hole.
I find I very rarely use the "aliquot" sizes of drills in my sets...1/16",1/8"
1/4" etc.
Why? Because I very rarely NEED a DRILLED hole of those sizes.
The hole sizes I need are..
Tapping sizes...Above 1/4" plus or minus .005" doesn't make a whole hoot of
PRACTICAL difference in the strength of the thread.
Clearance Holes...a few thou either way doen't affect function.
Fitting holes...Most often, drill, (again a few thou isn't important) bore or
open up with the correct reaming size. Then ream, bore, grind or lap to dead
size required.
By the way, if you need a hole closer to drilled size, be aware that, if you
drill it a few thou under and then follow through with the correct size of drill
it will cut pretty damn close to nominal diameter. If you "break" the corners of
the drill...stone a small radius on the outer corner...it will also give a
close-to-reamed finish.
Now before all the "Industrial" drill users jump down my throat..Yes I am aware
that OCCASIONALLY the case arises when it is NICE and MORE ECONOMICAL to be able
to drill pretty close to size in one shot. But please bear in mind that this is
REC.CRAFTS.Metalworking. Most people looking here for advice are just happy to
get a hole of ANY size when they first start out.
To them I say again. Take a drill and STUDY it, see how the same tool angles
you need on your turning tool are present and correct. They are just "twisted" a
little bit.
Take it to jour grinder and do a few "dry runs", before removing material, so as
to get the hang of the twisting and swinging motion involved. I generally use
the rim of the wheel for sizes between 1/8" and 1/2"..below or above that I find
it easier on the flat side of the wheel.
Grind a few drills! Test them! Grind them again. Practice makes perfect, it
doesn't take long to get the hang of it, and like riding a bike...You never
forget it.
Now, as to "Teensy Little" drills...
One of our regular jobs was drilling some kind of injector nozzle, No 80 size in
416 stainless. Hand feed on a Herbert #1 capstan lathe...not exactly a
"sensitive" feed.
Those drills were always sharpened, as required, by the operators (apprentices)
It was done in a few seconds with an eye loupe and a fine slip stone. Stone in
one hand, drill in the other, moving the drill on the stone. Once again, when
you got the HANG of it and KNEW WHAT YOU WERE TRYING TO ACHIEVE (geometry
wise)..it became a simple routine job and drill breakages were rare.
Robert Bastow

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: drill sharpening FAQ?
Date: Sat, 09 Oct 1999 21:09:02 GMT
Lordy, Lordy,..here we go throwing $300.00 or more of good tool money at a five
cent problem. One that doesn't work for "tiny drills and those above 1/2" to
boot!!
I think Darex are paying hidden commissions here!! (Just Kidding Grant) ;^)
I could teach anyone on this list how to grind a drill in less time than it
would take for them to drive down to the hardware store to buy the bolts to
fasten a darex onto the bench.
It is (Was?) considered a fundamental "first grade" skill among machinists.
Learned first couple of days on the job..not twenty years!!
Even today I doubt you will find a drill grinder in many Jobbing Shops, and any
so called "Skilled Machinist" that wandered around with a dull drill in hand
looking for a drill grinder..or. (Ferchrissakes)) a new drill, wouldn't make it
through his first day!!
teenut
Grant Erwin wrote:
> If you have twenty years to learn a motor skill, no wonder
> it seems like falling off a log for you.
>
> The best solution IMHO for a HSM is a Darex M3 setup. For about $300 you
> get drills that are sharpened RIGHT. Doesn't work for tiny drills or those
> larger than 1/2"

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: drill sharpening FAQ?
Date: Sun, 10 Oct 1999 03:48:00 GMT
I bet he had you drill a check hole with the drill to make sure it cut on size!
For the benefit of the doubters..How long did it take to get it right..the first
lesson?
How long does it take you now?
One of our regular jobs in the apprentice training school (All jobs were
regular production jobs...no "Test Pieces") was to drill #80 holes in some
stainless nozzles.
Usually you got a batch of 100 to do and you were issued with ONE NEW DRILL!
The job, which entailed machining complete, from barstock, including several
diameters, threaded section etc, was done on an OLD Herbert # 1 capstan
lathe..not a sensitive, high speed drilling machine.
The drill, which usually didn't cut worth a toss, right out of the packet, had
to be sharpened with a slip stone and an eye glass (loupe) You quickly got the
hang of it..and could feel/hear/sense when it was cutting right. Properly
sharpened, the #80 drill would drill 20 to 30 holes 1/8" through, before needing
to be touched up.
The incentive to "get it right"? First time you broke a drill the Forman would
look at you like something that crawled from under a stone and molested his
virgin daughter.
Most people only ever broke one drill!
Second time came the "Walk of Shame"!! You would be draped with a flour sack
"Poncho", a hangmans nose set loosely round your neck. You would be handed the
broken drill and "Banged around the shop" ie lead by the rope around the shop
while 50 or so Apprentices banged on their machine locker doors with anything
that came to hand!!
teenut
John Jacobs wrote:
>
> Good point teenut. My vo-tech teacher would take a jobber lenght drill,
> grind it flat, and have us grind it back. Of course we used a drill
> guage to keep the lip lenghts correct. After we did it, he would do it
> again, etc. What no one has mentioned is that as you resharpen a drill,
> the web gets thicker. Sharpening a drill, and thinning the web is on
> page two. How to read a steel rule is on page one.

Newsgroups: rec.crafts.metalworking
Subject: Re: drill sharpening FAQ?
From: Robert Bastow <teenut@home.com>
Date: Sun, 10 Oct 1999 06:09:45 GMT
Jim,
Sorry if I mispoke you!
Ref Microscope..I meant I have never used one to grind a drill..YET! I recently
acquired a Christen drill grinder, which is equiped with its own seting
microscope.
I hasten to add..lest I be misunderstood ;^) I bought it only because it looked
pretty, and it was lonely, and it was cheap, and it looked to have the makings
of a nice little T & C grinder..sort of a cross between a Deckel and a Quorn!!
I have used microscopes many times for other purposes..checking tool edges,
measuring details and lookig endlessly at micrographic samples of metal alloys
in the days when I *almost* became a Metallurgist.
Mater of fact I am watching Ebay now for a half decent stereo toolmakers
microscope..But not for grinding drills!! 8^)
teenut
mulligan@advinc.com wrote:
> In article <37FF7B4D.C1A1D17B@home.com>,
> Robert Bastow <teenut@home.com> wrote:
>
> > But I do strongly object to giving struggling amateur learners, on a
> > RECREATIONAL.CRAFTS.METALWORKING list the impression that they can't
> > grind a drill, perfectly satisfactorily, by hand and without a
> > microscope.
>
> Go back and read my comments - I was agreeing with you.
> Your condescention ill-suits you.
>
> > That, dear boy is BULLSHIT!
> > teenut
> > Who has never used a drill grinder or a microscope...
>
> You should give the microscope a try sometime. Actually
> quite valuable for getting a good view of lots of things like
> cutting edges.
>
> Jim

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: drill sharpening FAQ?
Date: Sun, 10 Oct 1999 20:03:58 GMT
What IS your problem Jim??
mulligan@advinc.com wrote:
> In article <38000D38.E3E64840@home.com>,
> Robert Bastow <teenut@home.com> wrote:
>
> > The drill, which usually didn't cut worth a toss, right out of the
> > packet, had
> > to be sharpened with a slip stone and an eye glass (loupe)...
>
> Hold on there. First you've never resorted to a microscope to sharpen
> a drill. Yet in the above narrative, there's the loupe.
Since when was a loupe a microscope??
> Hmm. Did you also walk 17 miles to school every day, in snow
> "up to here" wearing nothing but that flour sack?
Do I detect a hint of disbelief? Could that be because so many things are
outside YOUR obviously limited experience? Mockery as a tactic is a first
resort of an idiot and the last resort of a failure!
In actual fact it was eight miles and yes, we did walk it "Up to here in Snow"
Not every day..but often enough, when the buses couldn't get through.. a not
infrequent occurrence on the Yorkshire Moors. There were times when I would
have been damned thankful for an extra layer..sacking or otherwise! Kids didn't
have "Snow Suits" and Mommas with 4WD Broncos then!
> Any shop that would rather have it's workers re-sharpening
> drills like that (strictly a waste of time in a production environment)
> rather than making parts, is probably long since out of business.
Jim, I was talking of Forty years ago.!!
We were talking of a TRAINING CENTER!!
They were training SKILLED tradesmen..You know (Maybe) the kind of people that
produce the kind of equipment that your "Workers" need in todays "Production
Environment"
Incidently the company IS still in Business..and probably making similar parts
by better (production) methods tho' the quit training their own skilled people a
generation ago and probably Import all their production equipment as a
consequence.
It is called "Dumbing Down" and part of the reason is the short term kind of
"third quarter Bottom Line" thinking that you exhibit above. God knows what the
eventual cost will be!
We had been discussing whether it was POSSIBLE to sharpen a drill properly
without a Darex $300 whizz bang.
We have been discussing this on a News Group..where, by definition (
Rec.Crafts.Metalworking..not alt.ind.hightechproduction) most of the people are
just glad to get the drill to go around the right way and cut a hole.
The thrust of yourself, and other, even more supercilious and arrogant posters
has been that it is impossible to properly regrind a drill without a slew of
expensive equipment.
That is Bullshit as I have already stated. Just because YOU can't, doesn't mean
it is impossible..or even that damned difficult!
I think enough people with the skill to do it, have spoken up and perhaps
encouraged some of our newer comers to metalworking to go and try it for
themselves.
> Good drills are expensive - but like most tool steel, cheap stuff
> is no bargain.
Even brand new, top of the line, expensive drills, often don't cut worth a toss
straight out of the packet..I think that was confirmed by quite a few people
too!
teenut

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: drill sharpening FAQ?
Date: Mon, 11 Oct 1999 07:59:04 GMT
mulligan@advinc.com wrote:
> Robert Bastow
> > What IS your problem Jim??
>
> None whatever. Life's just grand.
Glad to hear it, last thing I want is, for what should be a professional
discussion to get out of hand and start to spoil anyone's day!
> > The thrust of yourself, and other, even more supercilious and arrogant
> > posters has been that it is impossible to properly regrind a drill
> > without a slew of expensive equipment.
>
> Here you are really off base, Robert. You mis-state my position
> completely. Of course one can grind
> a decent drill offhand.
Then I apologise Jim!!
SOMBODY said that and, in the convolutions of this thread I had come to believe
it was you!
(trust me..if it gets any more convoluted I will be writing nasty missives to
myself..and so will you!)
> The task becomes more complex as the
> size goes down, and at some point becomes impossible without
> some extra magnification. 1/8 - sure, that's easy. But I would not
> bother to do the ones in the 60 thru 80 index without some help.
No disagreement..unless you HAVE to! My point is that a lot of people on this
list have only the option of tackling it with no help, no aids, no skill and no
practice...or NOT DOING IT! What a tragic waste!
I can't be there to help them..but at least I can give them the confidence to
TRY..knowing that it CAN be done, It has been done, and by golly, if that old
fart teenut can do it SO CAN I!!
(Forgive me Jim..I am not SHOUTing..just putting emphasis on the key points!)
> Anyone who wants to learn this skill should start large - and I
> mean 1/2 inch and above. This is a great way to make long drills
> short.
I believe I learned on a 3/4" taper shank drill..it is a lot easier to see all
the angles and begin to understand how they work and interact.
By the way..we had a handy little dohickey to help get the drill lips level. I
have never heard it described before..
For the morse taper shank drills from 1/4" up to about 1" diameter, we had a
piece of 2" by 1/8" hot rolled steel strap..about 14" long. One end was bent at
right angles, about 2" from the end to form an L shape with one 12" upright and
a 2" horizontal. In the geometric center of this short leg was afixed a "dead"
center..not a lathe tailstock center!!...more like a 1/2" bolt, 1/2" long,
turned or ground to a 60 deg point (Approx...no great precision required) and
screwed in from the under side. Thats IT..toolmaking over!
In use the inner face of the upright was coated with whitewash (Never SAW
marking blue 'til I got in the toolroom!) The drill was ground, freehand, on
the FACE of the wheel (not the flat side)...care being taken to keep the POINT
angle as equal as possible on both sides..I'll tell you how to do THAT in a
moment..
Lets do that now in fact..
Jim, You are dead right about not being able to grind a drill without mechanical
help! Well here's how you create your own "6 Million Dollar Bionic Darex" ;^)
Let's assume we are going to sharpen a 3/8" diameter, 2MT shank drill..it is
about 8" long (these figures are arbitrary..I just want every one to have the
same mental picture of what I am describing.) We approach the wheel, which has
been dressed on its face, dead straight across with no grooves..(Ve SHOOT anyone
ve catch putting grooves in ze drill wheel!!..No Pity..No Prisoners..Ya!
Verdampt!)
(Sorry)...
The drill shank is held firmly in the RIGHT hand...ALL the movement and control
is imparted by the RIGHT hand. For the purposes of drill grinding, the left hand
could be...with benefit..a LUMP OF CLAY!!
It is from this "lump of clay" that we fashion the Bionic Darex".
Place your left hand thumb and finger tips LIGHTLY together..Relax the other
three fingers aand let them naturally curl against the palm of your hand. Let
the drill flute drop into the vee between thumb and fore finger and let the tip
of the finger "Find" the curve of the flute where it fits comfortably. The tip
of the thumb rests on the sharp junction ot the land and the flute, about an
inch back from the drill tip.
Now...SQUEEZE HARD!!! YOUCH!...I said it would be easier if it were clay! 8^)
Lift the drill from your fingers...see the GROOVE?...Drop the drill back in..it
locates within a thou or two! Magic?..Bionic at least! Squeeze again to set the
groove. You have created a customised drill guide that fits better that that on
any machine ever built! You can relax your grip now..feel how smoothly the
drill will ride back and forth, guided by the groove you have created for it.
Place the knuckles of your left hand, LIGHTLY on the ginding wheel tool rest,
and swing the drill shank, from left to right (using ONLY your right hand) and
push the drill lengthways though that groove in your fingers back or forth using
the groove to make the drill twist or "rifle" in your fingers. Do NOT move your
left hand in any way..it is made of clay remember!
UNTIL....
A) The drill axis is "eyeballed" to be at half the required point angle to the
wheel face...You can scribe or chalk reference lines on your grinder benchtop to
help you line this up..at least untill it become almost second nature.
B) The drill axis is dropped JUUUst below horizontal. This will ensure that
your soon to be ground drill lip will start with a "smidgin" of cutting
clearance.
(Ideally, and certainly for a beginner, the grinder rest should be set dead
radially to the wheel center and about half the drill diameter below the true
center of the wheel)
C) The two cutting edges of the drill..the straight, sharp bits, formed by the
junction of the flute and the back face (the only bit you grind), should be
horizontally disposed..with the edge uppermost on the side closest to your left
hand..the othe sharp bit of course, pointing downwards (Jeeze this would be a
lot easier with a sketch pad)
This I will call the SET or START position!
NOW, move your left hand for the first, last, and ONLY time during th is whole
exercise. GENTLY ease the cutting edge towards the spinning wheel, carefully
maintaining all the angles and orientations of the SET position..until the
cutting edge is JUST shy of touching the wheel. If you listen carefully you
will hear the tone of the entrained air, whistling through the narrowing gap.
You will hear a subtle but distinct change of tone JUST, I mean Just...a couple
tenths of a thou BEFORE the edge touches the wheel. STOP!!! FREEZE!! DO NOT
MOVE!!
Now, press the knuckles of your lump of clay..sorry, your left hand FIRMLY down
onto, into and around the grinding rest..establish a "Groove" on the back of
your hand as well as between your fingers.
We are now ready to grind, Your left hand locked to the drill and grinding rest
is otherwise quite relaxed..letting the drill slide, twist and tilt wherever
your right hand and the groove in your fingers tell it to go.
The actual grinding is a bit of an anticlimax.
You have previously studied a new drill point, you have read about clearance,
and cutting angles, and rakes and......
With the RIGHT hand in control, gently, kinda, lean forward... bending or
squeezing your arms hands and body..rather than actually moving them..untill you
take up that last couple of tenths and the wheel begins to cut. Let it
cut..don't force it, and dont' rush it..it really won't hurt anything if you
take a full minute Per pass per face. YOU and your "Bionic Darex" are totally
in control of that drill and the wheel..Forget the times when, close to panic,
you swung the drill wildly past the wheel, hoping to get "the dirty deed" over
with as quickly as possible.
Take your time, enjoy the moment, THINK about the shape you are trying to
generate. Just the one face is left to "Interpretation"...every other
aspect,angle, facet, what have you...Has ALREADY BEEN TAKEN CARE OF!! and is
locked in place under your control!
The right hand should perform a "Lower Quadrant sweep" for want of a better
term..An observer behind you would see your hand move from about 17 minutes past
the hour on a clock face, to roughly 25 minutes past. But it isn't a smooth arc
of a circle, more a sector of an elipse..You see, as your hand starts to drop
slowly, you are also rotating the drill in "the groove"..the first third of the
turn needs to maintain that very slight clearance angle on the cutting edge, and
not increase it too rapidly.
You need the clearance to cut..But too much at that point will WEAKEN the edge,
and cause the drill to snatch and chip...So the first part of the rotation is
ALMOST but not quite, just as though you were grinding a straight cone point on
the end of your drill. Only as you approach the second third, does your right
hand start to noticably drop..kinda "Catching Up" on the rotary
motion...increasing the clearance as it does.
In the last third of the rotaion the right hand drops quite rapidly..Thogh not
enough to catch the OTHER drill lip on the wheel..that lip is coming around
quite rapidly by now.
Above all, take your time, if it helps, move the drill one degree at a time, and
think ahead what shape or angle the next degree of cutting face
needs...Remember, you have control, and IT ain't going nowhere 'til you decide.
After a pass on one face, flip the drill in your "Bionic Darex" DO NOT MOVE
THAT LEFT HAND!!, return to SET position and repeat, the pass on the other face.
Having done a couple of passes on each face..it is now time to check the results
on our homemade "Optical Comparator"
(Sorry Jim I couldn't resist!!) ;^)
Rest the center hole in back end of the drill shank, on the center point of the
"Comparator" and use, first one and then the other drill lip to scribe a light
line on your whitewashed (OK Blue or red dyed) surface.
You will readily see if the lines coincide..if the lips are even..or not, as the
case may be.
Lets assume they are..Now look directly DOWN on the end of the drill to check
the clearances. HUH? How can you check radial clearance by looking it staight
in the face? Surely you need to look at it sideways?
Well no you don't...for once all thos interacting and confusing angle and faces
and clearances are going to work together in YOUR favor and make what could be a
tricky bit of metrology..quite simple. While we are looking at the end of the
drill, we will also check that the POINT ANGLE is correct too!!!
(Ok guys, leave quietly..teenut has finally lost it!!)
No really, trust me. IF you look straight down on the point of a well
sharpened, standard drill, you will see
the two cutting edges, joined by the CHISEL edge which crosses over the web of
the drill The angle fromed by the chisel edge to each cutting edge, should be
ABOUT 50 deg...anywhere between 40 and sixty is ok for a first attempt. (I can
hear the purists and theorists screaming and lighting up their flame throwers)
But believe me, get it in that ball park and your drill will CUT. If the angle
is too steep..you don't have enough clearance...negative clearance will give you
an angle event greater than 90 deg. Too MUCH clerance and the angle will appear
too shallow!
While looking at the end, check the point angle, How? Look down the axis of
the drill at the cutting edges. Are they straight? If so, your point is pretty
close to the right angle (As designed for that drill, by its manufacturer when
he set the helix angle and the cross section of the flute) If the edges appear
CONCAVE the point is too flat and if they appear CONVEX, the point is too
"Pointy"
If your drill passes all these tests, which take but a second or two to perform,
THEN IT WILL CUT..pretty close to size, without chattering, chipping,
overheating, wandering or seizing. I guarantee it!
Hey, thats a pretty good start for the first drill you ever ground! All it
takes now is a bit of practice for it to become second nature and almost as easy
with a little 'un or a big 'un!
Hey guys!
My apologies for "goin'on" but If it helps just one person to pluck up the
couragre and go hand sharpen his (or Her) first drill, by hand...
Then I hope you will bear with me.
It is late, I am tired and I am not even going to proof or spell check this,
'night all
teenut

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: drill sharpening FAQ?
Date: Mon, 11 Oct 1999 19:21:26 GMT
mulligan@advinc.com wrote:
> Quite a tutorial. Thank you for taking the time to put it here.
> It gives a good start, but really one has to ruin a boxfull of
> drills before it can be really understood.
I don't think that is the case Jim, Most 15 year old apprentices got it right
after a couple of tries..It isn't rocket science!
> Fortunately most of us have boxfulls of clapped out drills to
> start on.
Should have started earlier, Huh? ;^)
> I might add the following: When checking the included angle of
> the cutting edges it is helpful to light it properly. I like
> to have the drill itself in darkness, with a bright white or light
> colored background behind it, giving that optical comparo effect
> you mention. I find that if I can discern the flutes and so on
> it makes it tougher to look at *only* the angles and the relative
> lengths of the cutting edges. Sort of an optical illusion.
A bit of practice and you can do it (almost 8^) in the dark. Our apprentice
training shops were pretty dimly lit at best. In any case, a lot relies on the
"feel" especially with smaller drills (an older eyes I might add)
The whole point of the "Bionic Darex" is that, once "locked in" it is not a
lighting and vision dependent operation.
> I also have gotten into the habit of grinding two reliefs on the
> back of the edge. The first one provides the actual cutting
> relief, and the second one prevents the back edge from scuffing.
> The second one is a lot easier than the first because the angle
> is not a critical.
>
> This is not as pretty as a real 'twist ground' back relief, but
> works quite well for most applications.
Beauty is in the eye of the beholder..some people and drill grinding machine
companies swear by the "Two Facet" method. Others swear at it! Certainly the
edge isn't as strong and is more prone to dig in, catter and break down as a
consequence. My Christen is designed exclusively for two facet grinding..which
is maybe one reason why I may never use it for drills. It is designed for drills
only from .0020" to .025" diameter..but I still prefer to hand grind or stone!
Dammit it's faster!!
It is interesting to note, that the people who are probably the "Worlds Experts"
on drill pointing viz. The gundrill makers, use a properly relief ground cutting
edge geometry.
> Also important to *stone* the cutting edge before using. I like
> to stone along the edge, not across it.
Why, no other cutting edge is stoned along the edge! Enough research and
ecperience has shown that striations running parallel to an edge, weaken it more
than striations at right angles to it. Ask any woodworker, or knife maker.
Stoning along the edge of a metal cutting tool makes it more prone to edge pick
up/welding and all the horrors that attend it..ask any pro. turner worth his
salt!
If the technique is right and the wheel is right you shouldn't need to stone the
edge. Indeed, unless your stoning technique is dead on..chances are you will
blunt the drill!!
> Now, Robert, if you could do a treatise on thinning the web, that
> would be enjoyable to read.
Hmm! Here goes..
Bung the inside of the flute against the radius corner of the wheel, flip it
over and repeat for the other side. Inspect and correct or go drill the hole!
Yeh, I'm kidding..a bit! ;^) But on drills under 3/8" (For HSM purposes) web
thinning is more trouble than it is worth. Above about 9/16"..most HSMers are
better advised to pilot drill first..I do.
In between..the above technique has served countless thousands of machinists for
generations.
The point to watch is that the thinning is even..to eyeball standards and that
it not weaken the web too much..on jobber length drills there really is no need
to thin the web until you get to the last inch or so of flute. If you genuinely
manage to use, and grind a drill that far..you will have enough skill and
experience to be writing this piece!
If on the other hand you need a shorter drill..use a stub or screw machine
length..They start out with thinner webs.
> I have seen a very nice technique
> that not only thins the web, but creates a nearly-centercuttin
> second set of edges at the same time - but it requires a wheel
> with a nearly right angle to do so.
Split point drills..Hmm!
My Christen is specifically designed to do that, it needs the diamond wheel to
hold the square edge that you mention. Plus microscopic adjustments to do it
right.
Certainly not a technique for the HSM without spending a lot of good tool
money. $300 for Darex?..I have heard people swear BY them and AT them. A new
Christen will run in the $12.15000 range and we KNOW that will do it, first
time, every time! but had this one not "Fell off a truck in front of me and not
got broke" I wouldn't have sprung the thirty dollars of good tool money it cost
me.
I only bought it because I thought it had the makings of a little T&C
grinder..sort of a cross between a Deckel and a Quorn. If it can't "split
point" drills when I am done the conversion..then I am not going to loose a
minute"s sleep over it. So there! ;^)
Split point drills have a lot of claims made for them..The major one I hear, is
that they are self centering and don't need a center drilling operation first
and thus save an operation, and a tool change on a CNC machine.
Well (can't you hear 'ole teenut sucking his teeth over the validity or worth of
THAT one??"
If you have a CNC machine (Hands Up For A Head Count) and want a LOT of holes
(HUFAHC) and don't mind some of those holes being "just a few teeny thous or
tenths" off position (HUFAHC) and if you don't mind some of those holes being
the same "teeny bit" off size (HUFAHC) and if having come this far you are a
GENUINE HSMer (HUFAHC)..then I guess (who's left?) you have need for a Darex or
a Christen to do your split points!
For the rest, let's keep the good ol' twist drill in perspective. It is a means
of making a hole. Period!
If that hole is to put a (non-fitting) bolt through, lighten something, let
water out, or prepare the way for further operations, it has served its purpose
admirably. IMHO anything else is expecting way too much of it.
Any other "Holey" condition can better, faster, and certainly, more accurately,
be achieved by specialist, follow up operations with tools and techniques better
suited to the job. And, (he said grammatically correctly) And, if any of the
CNC, split point users who had their hands up earlier, expect that a drill ANY
DRILL, can replace, to name but a few, a boring head, reamer, roller burnisher,
or jig grinder Them I am afraid they are missing the whole point of this.
> Also, have you a recipie for those nice sheet metal drills that
> have the reverse angle cutting lips and a center pip - so they
> don't grab - they cut out small slugs? I've made a few of those,
> but they are a lot more hit-n-miss!
No recipe fot them Jim..But you've got to love 'em! I like the B&D bullet
points..I was fortunate enough to pick up a lifetime"s supply on ebay, cheap
cheap cheap I will meter those out for the job they do best..sheet metal, where
I can't get a unibit at it! I don't do any sheet metal work but once a blue
moon.
I can grind a workeable facimily by hand, on the corner of the wheel,,basically
a flat botton drill with a tit left on seems to work quite well. For wood work
I like brad points (if it is too small for a forstner) Those are ground the
same way..a flat bottom drill with a tit in the middle and a cutting skirt st
the rim.
In all the above, and earlier work, I have tried to stress, over and over again,
that this is not just my opinions..but my lifetime's experience as both a
"professional" metalworker, as a HSMer and as a long time teacher of "Machine
shop"..in the class room, on the floor AND on the Advisory Boards of Vocational
trainig Centers and Regional Apprentice Training Organisations
I have repeated, over and over again, that, in view of the forum, this is
TOTALLY slanted towards the HSMer, and my objective always has been, to simplify
(Not over simplify) and to debunk and demystify enough so that the newcomers
among us are encouraged to go "do it" without being afraid of the initial
failure that always preceeds success. As I said earlier..If just one
struggling, unsure, beginning HSMer gets to hand sharpen a drill and work his
way through a bit of metal to daylight on the other side..then, to me this will
all have been worth it.
I am WELL AWARE that I have, deliberately, made statements that my "Fellow Pros"
will cringe at, and would be all over me like white on rice..IN A DIFFERENT
FORUM. Hey, I would lead the wolf pack!!
But the real pros, share a lot of my concerns about the loss of skills and
training, and understand how difficult it is to put across, highly visual and
dexterous techniques using only the written word. I thank THEM for their
"silent" support.
They know too how difficult that is, without them becoming part of the
problem..The howling mob of "Pseudo Experts" who haven't heard a word I have
said, and never will.
To them I say..Step right up! .but remember it is a lot easier to make something
sound difficult, than it is to simplify it!
Talk to you later Jim,
teenut